1. Field of the Invention
The present invention relates to a gas adsorbing element which selectively adsorbs and removes active gases contained in inert gases such as air, especially harmful gases such as organic solvent vapor, bad odor material, etc., to obtain clean inert gases such as air.
2. Description of the Prior Art
Zeolite is a molecular sieve and is used as an adsorbent because it mainly consists of aluminosilicate. Zeolite also selectively adsorbs water and other gas molecules such as organic solvent vapor, in accordance with the diameter of the molecules, making good use of the difference in diameters of micropores which are formed by elimination of crystal water.
A rotative reactivation type dehumidifier element has been proposed in Japanese Patent Publication No. 19548/1979 (laid open to the public without examination) which consists of a corrugated and laminated cylindrical honeycomb-structure made of sheets of asbestos paper, glass fiber paper, and etc., with a molecular sieve, for example, 4A, 13X, etc., attached to it. Also in Japanese Patent Publication No. 240921/1988 (laid open to the public without examination) a honeycomb-structure dehumidifier element is proposed which is made by adding a binding agent to synthetic zeolite powder of, for example, A type, X type, Y type, or natural zeolite powder such as mordenite and formed, for example, by extruding, press forming, or some other similar method. On the other hand, a honeycomb-structure element is proposed in Japanese Patent Publication No. 50068/1978 (laid open to the public without examination) as a rotative adsorbing element that adsorbs and separates organic solvent vapor, bad odor gas and other gases from the air. The honeycomb-structure element set forth in this publication is made of paper containing fibrous active carbon.
The above mentioned zeolite is able to selectively adsorb gas molecules in accordance with its molecular diameter. In adsorbing/separating organic solvent vapor, bad odor gases and other gases from the air, water vapor is always adsorbed together with organic solvent vapor, bad odor gas and other gases because there is always water vapor coexisting with the air. The molecular diameter of water is 2.8 Å. The molecular diameter or organic solvents or bad odor gases are all larger than that of water. For example, the molecular diameter of benzene is 6.7 Å, that of cyclohexane is 6.1 Å, etc. Therefore, zeolite can adsorb and separate water only but not organic solvent vapor or bad odor gas. Rather, water vapor is preferentially adsorbed and adsorption of organic solvent vapor or bad odor gas is obstructed by the adsorbed water molecules. Therefore, when the absolute humidity of process air is high, zeolite cannot efficiently adsorb and separate organic solvent vapor or bad odor material.
Active carbon is a hydrophobic adsorbent and preferentially adsorbs non-polar molecules such as hydrocarbon. However, it is flammable and has a danger of catching fire when hot air about 130° C. is used for reactivation. Also some types of adsorbed solvent generate high adsorption heat and the adsorbing element has a danger of catching fire. Thus, it is extremely difficult to use. Moreover, the adsorbing capability of the element decreases by the adsorption of oil. After being used for a certain period of time, regeneration of the element at a high temperature of approximately 300° C. is necessary. This active carbon element, however, has a defect such that during high temperature regeneration hot air cannot be used; rather, superheated water vapor should be used for regeneration.